Evolution of Pulmonary Embolism Response Teams in the United States: A Review of the Literature

Pulmonary embolism (PE) is a significant cause of cardiovascular mortality, with varying presentations and management challenges. Traditional treatment approaches often differ, particularly for submassive/intermediate-risk PEs, because of the lack of clear guidelines and comparative data on treatment efficacy. The introduction of pulmonary embolism response teams (PERTs) aims to standardize and improve outcomes in acute PE management through multidisciplinary collaboration. This review examines the conception, evolution, and operational mechanisms of PERTs while providing a critical analysis of their implementation and efficacy using retrospective trials and recent randomized trials. The study also explores the integration of advanced therapeutic devices and treatment protocols facilitated by PERTs. PERT programs have significantly influenced the management of both massive and submassive PEs, with notable improvements in clinical outcomes such as decreased mortality and reduced length of hospital stay. The utilization of advanced therapies, including catheter-directed thrombolysis and mechanical thrombectomy, has increased under PERT guidance. Evidence from various studies, including those from the National PERT Consortium, underscores the benefits of these multidisciplinary teams in managing complex PE cases, despite some studies showing no significant difference in mortality. PERT programs have demonstrated potentials to reduce morbidity and mortality, streamlining the use of healthcare resources and fostering a model of sustainable practice across medical centers. PERT program implementation appears to have improved PE treatment protocols and innovated advanced therapy options, which will be further refined as they are employed in clinical practice. The continued expansion of the capabilities of PERTs and the forthcoming results from ongoing randomized trials are expected to further define and optimize management protocols for acute PEs.


Introduction
Pulmonary embolism (PE) affects between 350,000 and 900,000 individuals annually in the United States.It is the third leading cause of cardiovascular death, with a 30-day mortality rate of 10% and a 1-year mortality rate of up to 20% [1][2][3][4][5].In clinical settings, PEs are classified using the PE Severity Index (PESI) into three categories-low risk, submassive/intermediate risk, and massive/high risk-based on clinical features such as hypotension, need for vasopressor support, and right-ventricular strain or dysfunction [6,7].The Wells and Geneva scoring systems, echocardiograms/bedside point-of-care ultrasounds, spiral computed tomography angiography (CTA) scans, and PE Rule out Criteria (PERCs) are also used when a diagnosis is not immediately clear.Once a PE diagnosis is confirmed, the universally accepted initial treatment is systemic anticoagulation (unfractionated heparin, argatroban, bivalirudin, etc.).More aggressive interventions, including systemic thrombolysis, catheter-directed therapy (lytic or thrombectomy), surgical embolectomy, and mechanical circulatory support, are reserved for severe cases according to established guidelines [8] [Tables 1 and 2].
While treatment protocols for massive/high-risk and low-risk PEs are generally standardized, the approach to managing submassive/intermediate-risk PEs is less clearly defined [Table 3].This is further complicated by discrepancies and variations among guidelines from various societies, including the American Heart Association (AHA) [9], American College of Chest Physicians (ACCP) [10], American Society of Hematology (ASH) [11], and European Society of Cardiology (ESC) [12].
This variability in management, along with the urgent need to devise a treatment plan, forces clinical teams to rapidly evaluate and decide on the best course of action for these complex cases, often without a clearly superior treatment option.Variations in management are further influenced by the expertise and resources available at local institutions.Consequently, physicians must often weigh the risks of rapidly initiating potential therapies-such as bleeding, procedural complications, and mortality-against the dangers of treatment delays [13].
The past decade has seen the emergence of Pulmonary Embolism Response Teams (PERTs) in reaction to the abovementioned challenges, with a particular focus on addressing intermediate and high-risk PEs, a class IIa recommendation by the European Society of Cardiology [12].These multidisciplinary units are designed to rapidly and comprehensively manage acute pulmonary embolisms (PEs).Comprising specialists from various fields, including emergency medicine, pulmonology, critical care, radiology, interventional radiology, interventional cardiology, cardiothoracic surgery, and hematology, PERTs guide treatment decisions based on the patient severity, ranging from anticoagulation to fibrinolysis, catheter-directed therapies, or surgical embolectomy.We conducted a review of the current trends in the management and treatment of PEs, focusing on data related to PERTs.This review aims to examine the conception, evolution, implementation, and effectiveness of PERTs, as well as discuss the current and future state of these programs based on available literature.

Conception and Evolution of PERT in the United States
The first Pulmonary Embolism Response Team in the United States was established in 2012 at Massachusetts General Hospital, affiliated with Harvard Medical School.This multidisciplinary team, composed of specialists from cardiovascular medicine, cardiothoracic surgery, emergency medicine, pulmonary and critical cares, vascular medicine, and radiology, was designed to provide real-time, consensus-driven management recommendations for patients with massive and submassive PEs.
Initially, a PERT was activated via telephone for a confirmed or suspected severe PE.A designated physician member would evaluate the case, considering patient hemodynamics, clinical characteristics, and available imaging to determine the necessity of convening a full team meeting.This physician also had the authority to mobilize essential resources, such as the cardiac catheterization lab or operating room and associated staff, depending on the decided course of treatment.
The benefits of PERTs were demonstrated through a case series of two complex situations in which rapid, expert consensus was crucial because of the lack of clear evidence on available treatment options [14,15].In these cases, the PERT facilitated the inclusion of additional specialties, such as OBGYNs, maternal-fetal medicine, vascular surgery, and structural heart, to formulate optimal treatment plans.One remarkable instance involved coordinating expedited care for a patient presenting at an external hospital, showcasing a PERT's capability of extending its expert management to more complex, time-sensitive cases, even beyond its home institution.
This pioneering initiative laid the groundwork for the formation of the National PERT Consortium in 2015, when physicians-experts met in Boston, Massachusetts, to create a collaborative environment to guide treatment by PERTs and medical institutions around the world [8].The mission of this international nonprofit organization was "to facilitate the exchange of ideas and information related to the care of patients with PE, and to advance the science of PE care by performing research, developing advanced treatment protocols, and educating clinicians and community members".At that meeting, the National PERT Consortium released an executive summary to guide the diagnosis and treatment (including advanced therapies) for patients presenting with an acute PE.
Physician attendees at the 2015 National PERT Consortium were also surveyed to collect responses regarding treatment of choice for various clinical scenarios to guide clinical practice.For example, a patient with a high-risk PE, low bleeding risk, right-ventricular dysfunction, and a right atrial clot was deemed to be an acute submassive, high-risk PE in line for surgical embolectomy by 77 respondents (88% of survey respondents) [8].However, this survey did note that respondents with access to PERT programs were more likely to suggest interventional and surgical therapies to treat patients.Since then, research revolving around PERT programs in the United States has advanced greatly with numerous retrospective trials and active randomized control trials.
To follow-up on the evolution of PERT programs across the nation, Barnes et al. surveyed active National PERT Consortium members on their respective institutions.An online questionnaire administered to 31 institutions (of which 19 had PERT programs) noted that most PERTs involved 3-5 different specialties which worked together primarily via telecommunication (12/18, 67%).Nearly 90% of these centers offered 24/7 advanced therapies albeit with variations regarding individual steering committee members [16].Interestingly, many programs (nearly 50%) offered dedicated "PERT clinics" for patients to follow-up in after hospitalization.
The first reports regarding PERTs were published around 2018 by Rosovsky et al., examining a 10-year analysis regarding outcomes at a tertiary-care institution [17].In their study, Rosovsky et al. compared the pre-and postinterventions of a PERT program against two prior studies with a control cohort of PE patients who were seen in their institution's emergency department (the prospective safe pulmonary embolism emergency department discharge (SPEED-D) study and the retrospective, SPEED-D(R) study).Their study identified 212 patients before a PERT intervention and 228 patients after a PERT intervention who met the inclusion criteria, and they noted that the proportion of patients undergoing catheter-directed therapy (10 [1%] vs. 31 [14%], unadjusted p < 0.0001) and any advanced therapy (19 [9%] vs. 44 [19%], unadjusted p = 0.002) was higher in the post-PERT group.Thus, noting that PERT increased the use of catheter-directed interventions and additional advanced therapies with no associated changes in bleeding or mortality for patients with massive and submassive PE.
The evolution of PERT was further accelerated by the COVID-19 pandemic because of the pathophysiologic and thrombogenic nature of COVID-19 infection and resultant downstream effects including sepsis and coagulopathy [18].The position of the aforementioned paper recommended that hemodynamically stable patients presenting with COVID-19 infection should be managed with anticoagulation alone while unstable patients or patients pending imminent deterioration should be considered for thrombolysis.Catheter-based thrombolysis and/or surgical embolectomy was cautiously recommended when no other alternatives were feasible because of concerns about viral contamination of the operating rooms and catheterization labs.In one prior report from an urban tertiary-care center from a 2-month period in 2020, there was a statistically significant decrease in catheter-directed therapies (5.5% vs. 23.1%,p = 0.02) during the COVID-19 pandemic with a clinically significant trend toward systemic fibrinolytic therapy during the same time period (13.5% vs. 3.9%, p = 0.3) [19].Nevertheless, PERT program utilization was nearly three-fold higher during the study time.
Since the pandemic, PERTs have become more commonplace in both university and community medical centers [15,20].Studies have investigated the utilization and outcomes of PERTs, with one paper, by Myc et al., noting that the rate of mortality significantly decreased with the adoption of a PERT program without additional increases in hospitalbased costs or lengths of hospital stay [21].Their team further noted a significant decrease in 30-day readmission rates in patients who had been treated through a PERT program (nearly 10%, p = 0.047).
To facilitate the treatment of patients at PERT-capable facilities with options for advanced therapies, Rali et al. previously enumerated a flow pathway for non-PERT-capable facilities to create an "Interhospital Transfer of Patients With Acute Pulmonary Embolism", with specific protocols on how to manage acute PEs with advanced management, such as critical care and vasopressor support [22].Further, Rosovsky et al. also published a treatment algorithm on how to escalate from anticoagulation to advanced therapies in cases of acute PE through the use of clinical guidelines and case-based approaches [23].

Outcomes of PERT
PERT programs include individuals from various specialties who all typically participate in the initial and long-term management of PEs.These specialties include pulmonology, hematology, cardiology (invasive and noninvasive), radiology (diagnostic and interventional), emergency medicine, and cardiothoracic surgery.This team collaborates to assess and manage patients with an acute PE, particularly those who are hemodynamically unstable or have a high risk of complications.The response is coordinated through a centralized communication system, often activated by a single-caller paging system to create a treatment plan by pooling resources.In PERT programs, the severity of an embolism and patient-specific factors are evaluated to tailor therapy.This is conducted through a standardized protocol that streamlines care and reduces the variability in treatments with the goal of improving outcomes [15,24].
A main objective of PERT implementation is to diagnose and effectively triage highrisk patients with a massive PE before clinical deterioration to obstructive shock and/or cardiac arrest.Bedside point-of-care ultrasounds or echocardiograms may be used to immediately triage patients, and this has previously been reported to have a sensitivity of 74%, specificity of 95%, positive predictive value of 95%, and negative predictive value of 75% in diagnosing pulmonary embolisms [25].CTA should be pursued if point-of-care ultrasounds or echocardiograms are equivocal or clinical suspicion of PE is high.In such patients, systemic thrombolysis through peripheral access is the treatment of choice in the absence of any absolute contraindications (Tables 1 and 2).While performing this triage, PERT members also evaluate patients for candidacy for veno-arterial extracorporeal membrane oxygenation (VA-ECMO), which may function as a bridge to additional therapies such as catheter-based interventions and surgical embolectomy [26].It should be noted that systemic thrombolysis does not preclude future cannulation to institute VA-ECMO.Surgical embolectomy is the first-line treatment of choice for high-risk patients with massive PEs presenting with a clot in transit or a right-ventricular thrombus.The SPEAR working group evaluated 214 patients with an acute PE treated with surgical embolectomy and noted a mortality rate of 11.7%.They further noted that mortality was highest among those patients who experienced perioperative cardiac arrest [27].A recent meta-analysis by Maqsood et al. pooled 492 patients with a clot in transit and a PE and noted that weighted mortality for anticoagulation alone was 35% (95% CI 21-49%), surgical thrombectomy was 31% (95% CI 16-47%), catheter-based thrombectomy was 20% (95% CI 6-34%), and systemic thrombolytic therapy was 12% (95% CI 5-19%) [28] [Table 2].
There are minimal trials comparing outcomes post-PERT versus those pre-PERT with most studies employing observational data from prior studies to create comparative arms.One of the longest PERT study periods to date was conducted by Rosovsky et al., 2018 and was a 10-year analysis of changes in treatment outcomes after establishment of PERT.Their team utilized a pre and postintervention study using an interrupted time series design to compare PE patients pre-PERT (2006-2012, n = 212) vs. post-PERT (2012-2016, n = 228) [17].
Their team found that post-PERT patients were more likely to undergo catheter-directed therapy (1% vs. 14%, p ≤ 0.0001) or any advanced therapy (19 [9%] 3], While this study did not evaluate PERT programs, its results influenced treatment algorithms for PERTs across the United States.In this study, there was a lower risk of death or hemodynamic decompensation in the fibrinolysis group with tenecteplase and heparin (13/506, 2.6%) versus in the placebo group which was treated with heparin alone (28/499, 5.6%) (odds ratio (OR) 0.44, 95% confidence interval (CI) 0.23-0.87,p = 0.02); however, the fibrinolytic group had a higher risk of bleeding (extracranial bleeding, stroke, etc.).Extracranial bleeding occurred in 6.3% of patients in the tenecteplase group compared to 1.2% in the placebo group (p < 0.001).Stroke occurred in 12 patients (2.4%) in the tenecteplase group (10 of which were hemorrhagic), while only 1 patient (0.2%) in the placebo group had a stroke (which was hemorrhagic, p = 0.003).By day 30, the mortality rate was 2.4% in the tenecteplase group and 3.2% in the placebo group (p = 0.42).
Among the numerous retrospective studies comparing pre-PERT and post-PERT metrics, the data are mixed [Table 2].Some studies report a decrease in mortality following the formation of a PERT, while others find no significant difference.For instance, one study documented a decrease in in-hospital mortality from 16.5% pre-PERT to 9.5% post-PERT (p = 0.025), a median decrease of 3 days in total length of stay (LOS) (p < 0.001), and a reduction in ICU LOS by a median of 1.5 days (p = 0.023) [38].Another study comparing outcomes for pre-PERT (n = 884) and post-PERT (n = 1158) patients presenting with a PE found no difference in PE-related mortality regardless of PERT activation (2.6% vs. 2.9%, p = 0.89); however, they observed a decrease in the use of systemic thrombolysis (3.8% vs. 2.1%, p = 0.02), a decrease in the placement of IVC filters (10.7% vs. 6.9%,p = 0.002), and an increase in catheter-directed therapies (1.3% vs. 3.3%, p = 0.05) [36].A similar prospective review of patients with an imaging-confirmed PE in 2019 noted that of 307 patients, a PERT was activated for 22.5% and that advanced therapy use was significantly higher in the PERT cohort (35% vs. 2%), with no difference in major bleeds when comparing PERT activation against standard care [40].This is in contrast to a retrospective review of 201 patients with PERT activations at a major teaching hospital in New York City, which noted that 16 patients (8.7%) had a PERT activated because of massive PEs but that the majority of patients were treated without invasive intervention (91.4% 95% CI 87.1-95.7%)[34].
In a separate study of 769 inpatients with a PE, researchers found that post-PERT patients had lower rates of major or clinically relevant nonmajor bleeding (17.0% vs. 8.3%, p = 0.002), a shorter time to therapeutic anticoagulation (16.3 h vs. 12.6 h, p = 0.009), and decreased use of inferior vena cava filters (22.2% vs. 16.4%,p = 0.004).Although an increase in the use of catheter-based therapy was noted, it was not statistically significant.Notably, there was a significant decrease in 30-day mortality (8.5% vs. 4.7%, p = 0.03), which was even more pronounced among intermediate and high-risk patients (10.0% vs. 5.3%, p = 0.02) [31].
When assessing PERT activation during the COVID-19 pandemic in New York City, one academic center, which had 82 activations between 1 March and 30 April 2020, noted that there were more PEs during the pandemic but fewer PERT activations (26.8% vs. 64.4%,p < 0.001) despite similar case characteristics [55].They further noted that patients with PERT activations were more likely to be female, have a history of DVT, or a negative COVID polymerase-chain reaction test.This is in line with COVID-19-era recommendations that suggested careful patient selection for mechanical and surgical therapies to reduce facility contamination [19].
A smaller study at a tertiary-care center in Philadelphia analyzed 52 PERT activations postimplementation.In their cohort, 57.7% of cases were treated with anticoagulation alone, while 30.8% underwent catheter-directed thrombolysis.Although patients who underwent catheter-directed thrombolysis had a shorter intensive-care unit LOS, the difference was not statistically significant, and similar bleeding rates of approximately 6% were observed in both groups [32].Another study from a tertiary-care hospital in Minnesota compared the following three periods of PE presentations: historical model, postconsensus-based treatment algorithm implementation, and post-PERT.There was a notable increase in the use of reperfusion therapy, both systemic thrombolysis and catheter-directed therapies, from 4.7% at baseline to 8.2% with the treatment algorithm and then to 16.1% with PERTs.This study also reported a statistically significant decrease in the length of stay by nearly 2 days [37].Researchers at the University of Rochester Medical Center conducted an observational analysis of 137 pre-PERT-and 231 post-PERT-era patients with intermediate/high-risk PEs, observing a reduced 6-month mortality (14% vs. 25%, p = 0.025) and decreased LOS (6.5 days vs. 9.1 days, p = 0.007), and they found that an earlier diagnosis significantly impacted survival rates, with the risk of mortality decreasing by 5% for each hour earlier the diagnosis was made [41].A single-center experience published at Cleveland Clinic noted that of 134 PERT activations between 2014 and 2016, PE was confirmed by imaging in 118 cases (88%), 14 patients (12%) were treated with catheter-directed therapies, 6 (5%) received full-dose systemic thrombolysis, 16 (13%) received half-dose systemic thrombolysis, and 10 (7%) underwent either surgical or mechanical thrombectomy.They noted zero bleeding events in patients regardless of systemic thrombolysis dosage [29].Another study analyzed 279 patients who presented with PE, with a PERT activated for 133 (47.6%) of these cases.This study found reductions in both in-hospital (2% vs. 5%; p = 0.2) and 30-day mortality (2% vs. 8%; p = 0.06), although the 12-month mortality rates were similar between the groups (7% vs. 8%; p = 0.7) [56].
These studies offer insights into the benefits observed following the implementation of PERT programs across the United States, with similar findings reported internationally.In Spain, one small study involving 78 PERT activations compared to historically matched controls noted a significant reduction in 12-month mortality (9% vs. 22.2%, p = 0.02) [57].Additionally, a study in Singapore reported decreased LOS and increased use of reperfusion therapy, without a corresponding increase in significant bleeding or changes in survival rates at discharge [58].
A recent meta-analysis found no difference in mortality when comparing the pre-PERT (357/3319, 10.8%) and post-PERT eras (265/3408, 7.8%) [risk ratio (RR) 0.89, 95% CI 0.67-1.19].However, for patients specifically classified as intermediate or high risk, the mortality rate tended to be lower in the PERT era (142/1327, 10.7%) compared to the pre-PERT era (131/875, 15.0%) (RR 0.71, 95% CI 0.45-1.12).Additionally, the use of advanced therapies was higher (RR 2.67, 95% CI 1.29-5.50)and the in-hospital LOS was shorter by an average of 1.6 days [59].The use of systemic thrombolysis and advanced therapies is an advantage of multidisciplinary PERTs especially considering that the International Cooperative of Pulmonary Embolism Registry and prior reports have noted as many as 70% of patients with a massive PE do not receive thrombolysis [60].As more institutions join the PERT Consortium, the accumulation of data and the expansion of patient studies will enhance our understanding not only of how PERT is improving outcomes but also of which advanced therapies experts and evidence-based practices specifically recommend.
A retrospective review by Ardeshna et al. evaluated 817 patients (168 pre-PERT and 649 post-PERT) and noted that there was a decrease in advance therapy use (16% vs. 7.5%, p = 0.006), specifically catheter-based therapies (8.5% vs. 2.2%, p = 0.008) and IVC filter placement (5.3% vs. 3.2%, p < 0.001) in the post-PERT group [42].A meta-analysis by Hobohm et al. included 22 original studies and 4 surveys with a total of 1532 intermediaterisk and high-risk patients evaluated by PERTs, and they noted that the overall mortality rate was 10%; however, when analyzing 9 controlled studies, there was no difference in mortality risk (risk ratio 0.89 95% CI 0.67-1.19)when comparing pre-PERT-and post-PERTera patients [59].These data are in contrast to prior presented reports and support the notion that PERT programs vary across centers while adhering to national guidelines.An etiology of these differences may stem from variations in the structures and responsibilities of PERTs across centers, including which specialists are available at local hospitals and other resource considerations [61].
From the perspective of emergency-room settings, a retrospective analysis of 425 patients treated by PERT programs over a 4-year time period noted that there was a decrease in primary endpoints (all-cause death, major bleeding, and venous thromboembolism) at 30 days (16.3% in 2015 vs. 7.1% in 2019), which persisted to 6 months (primary event rate 0.37, 95% CI 0.19-0.71)[43].When comparing PERT activations by origin (emergency room vs. critical care unit vs. inpatient floors), one study found that activations from the ED (n = 283, 88/4%) or floor (n = 100, 74.6%) were more likely to be for confirmed PEs than activations from the ICU (n = 63, 58.9%; p < 0.0001) [44].The ED was noted to have more PERT activations at night.Notably, the most PERT activations for massive PEs originated from a critical care setting (n = 41, 65.1%).Patient characteristics that have been previously studied and associated with PERT activation include vascular disease, pulmonary disease, central PE, and concurrent DVT, among other conditions, with one study commenting that only 15% (56/374) of low-risk PE patients triggered a PERT activation [45].An opportunity to improve appropriate PERT activation lies in education and awareness.This has been documented in a prior study that noted education regarding PERT implementation programs have led to improved rates of providers identifying markers of high-risk PE and increased comfort in handling such cases [47].
Current advanced therapies for pulmonary embolism include systemic thrombolytic treatments with recombinant tissue plasminogen activators (tPAs), such as alteplase and tenecteplase, alongside newer device-based therapies.Although device-based therapies are relatively recent and have limited randomized controlled trial evidence supporting their use, their adoption has significantly increased following the implementation of PERTs, as demonstrated by the studies mentioned above.
Among the devices used for catheter-directed thrombolysis, the EkoSonic Endovascular System, or EKOS (Boston Scientific, Marlborough, MA, USA), was the first to gain FDA approval.This ultrasound-assisted catheter delivers thrombolysis directly at the PE site and is supported by a few randomized trials comparing it to anticoagulation or standard catheter-directed thrombolysis [46,[62][63][64].The Bashir Endovascular Catheter (Thrombolex) also delivers local thrombolysis through multiple ports and its efficacy is supported by several trials [48,65].
There are also devices which have been designed specifically for catheter-directed thrombectomy.The FlowTriever system (Inari Medical, Irvine, CA, USA), a syringe-based suction catheter, is used to retrieve clots and is supported by two nonrandomized trials [66,67].The Indigo Aspiration System (Penumbra, Inc., Alameda, CA, USA), a continuous aspiration catheter system, has been validated in a clinical trial, demonstrating its efficacy [68].Another FDA-approved device, the AngioVac (AngioDynamics, Latham, NY, USA), is a closed venous-venous system that uses extracorporeal circulatory support for PE extraction.AngioDynamics has also released the AlphaVac, which operates similarly but without the use of return cannulas.These devices provide PERT programs worldwide with additional options that can expedite and enhance treatment outcomes for pulmonary embolism.
The benefits of PERT are multifold and are linked to efficiency in the emergency department, decrease in utilization of resources, improved collaboration across services (emergency medicine, radiology, vascular surgery, interventional cardiology, interventional radiology, cardiothoracic surgery, vascular medicine, critical care, and hematology, among other specialties) and improved mortality benefit [69].The main downside of implementing PERT programs is the cost to develop the program, increased administrative burden, and complexity.Initiating PERT programs requires coordination across medical specialties with the creation of an interdisciplinary team with a new call system to ensure 24/7 access to PERT capabilities [70].

Future Directions
The limitations of PERT programs are primarily linked to their relative novelty [33].As PERT programs have developed extensively over the past decade, insufficient pre-PERT data exist to compare against current treatment outcomes.Similarly, randomized trials have also been limited because of the lack of an adequate patient cohort.Another limitation of PERT programs, as previously mentioned, is the increased administrative burden, which can lead to a more arduous multidisciplinary process to finalize treatment plans and potentially lead to delayed care.Further, many PERT programs are currently located in tertiary-care centers, which frequently offer invasive treatment courses that may otherwise not be as accessible at community sites, skewing PERT treatment data.The data are also evolving regarding the treatment of "low-risk" PE, which is a group of patients for whom guidelines are not as well developed [50].Finally, insufficient long-term data exist on PERT management to determine the longitudinal impact of surgical vs. catheter-assisted therapies vs. fibrinolysis over time.
As of 2024, there are over 100 medical centers that have joined the National PERT Consortium, which has led to the creation of a comprehensive network of physician leaders across specialties to tackle the problem of acute PE care.There are currently three randomized trials sponsored by the National PERT Consortium, which have previously been described [52], as follows: (1) APEX-AV, (2) HI-PEITHO, and (3) STORM-PE.
The evidence is limited regarding direct head-to-head comparisons of treatments for patients with a moderate-or high-risk pulmonary embolism (PE), for which anticoagulation alone may be insufficient, and some form of advanced therapy is necessary.The PEERLESS clinical trial, which was recently initiated and is currently enrolling patients, addresses this gap.It compares large-bore mechanical thrombectomy using the FlowTriever System (Inari Medical, Irvine, CA, USA) with catheter-directed thrombolysis (CDT).Patients are randomized in a 1:1 ratio, and the outcomes include all-cause mortality, bleeding, clinical deterioration, and length of hospital stay.This trial will provide valuable evidence to guide the management of complex PEs once a PERT has decided to escalate treatment [49].A similar trial that evolved from PEERLESS, the PEERLESS 2 trial (RCT of FlowTriever vs. anticoagulation alone in pulmonary embolism) is currently enrolling patients to understand treatment outcomes in intermediate-risk PEs [53].
As we look to the future, PERT programs will become commonplace in medical centers around the world, offering patients presenting with an acute PE the opportunity for standardized medical care regardless of the center.

Conclusions
Pulmonary embolism response teams (PERTs) have emerged as a critical innovation in the management of acute pulmonary embolism (PE), particularly for complex and high-risk cases.Since their inception in 2012, PERT programs have demonstrated significant benefits, including increased utilization of advanced therapies, reduced treatment variability, and improved patient outcomes.The multidisciplinary nature of PERTs ensures comprehensive, real-time decision making, which is crucial for optimizing treatment strategies and reducing mortality rates.Despite some limitations, such as the need for more randomized trials and long-term data, the positive impact of PERTs are evident.As PERT programs continue to expand globally and more institutions join the National PERT Consortium (https://pertconsortium.org/ accessed on 4 July 2024), the future of PE management looks promising, with ongoing research and collaboration set to further refine and enhance treatment protocols.
Funding: This research received no external funding.

Data Availability Statement:
No new data were created or analyzed in this study.Data sharing is not applicable to this article.

Table 2 .
Recent studies on pulmonary embolism response teams.

Table 3 .
Recent trials on pulmonary embolism therapies.
vs.44 [19%]), primarily amongst patients with submassive PE [Table 2].A landmark study in the treatment of acute PE was a randomized, double-blind trial (Fibrinolysis for Patients with Intermediate-Risk Pulmonary Embolism, PEITHO) by Meyer et al., in 2014, published in the New England Journal of Medicine, which assessed fibrinolysis for patients with an intermediate-risk PE [54] [Table